thumbnail/waveform generation

io/previewgenerator.h

@@ -3,11 +3,18 @@
 
 #include <QThread>
 
+struct Media;
+struct MediaStream;
+struct AVFormatContext;
+
 class PreviewGenerator : public QThread
 {
 public:
     PreviewGenerator(QObject* parent = 0);
-    void run() override;
+    void run();
+    MediaStream* get_stream_from_file_index(int index);
+    Media* media;
+    AVFormatContext* fmt_ctx;
 };
 
 #endif // PREVIEWGENERATOR_H